Protecting the Hunters

Hunter class (BAE Systems)
BAE Systems’ ‘Hunter’ class frigate for the Royal Australian Navy is based on the company’s ‘Type-26’ class Global Combat Ship destined for the Royal Navy.

The Royal Australian Navy is forging ahead with its acquisition of new frigates. What electronic warfare capabilities might protect these new ships?

The Royal Australian Navy (RAN) will start to commission the first of three ‘Hunter’ class frigates in 2031. These vessels are based on BAE Systems’ Type-26 class Global Combat Ship design. Alongside the RAN, eight similar ships will furnish the Royal Navy. These will replace its Type-22 Broadsword and Type-23/Duke class frigates.

Information is sporadic on the Electronic Warfare (EW) apparatus furnishing the new Australian ships. Open sources confirm that one system will be BAE Systems’ Nulka Radio Frequency (RF) decoy. Nulka was developed in Australia. The innovative decoy is designed to defeat radar-guided Anti-Shipping Missiles (AShMs). It achieves this by using a Digital Radio Frequency Memory (DRFM). Nulka has a rocket motor which propels the decoy some distance from the ship. The decoy is launched when the ships’ radar and/or Electronic Support Measure (ESM) detects an incoming AShM. After launch, the DRFM is activated. This detects radar transmissions from the AShM. The signals are sampled and are then manipulated and transmitted back to the missile.

The clever thing about Nulka is that the DRFM can alter the radar’s transmissions. By manipulating the radar signals the decoy can convince the radar that its targeted ship is moving at a particular speed. Likewise, the hostile radar waveforms can be altered to make the missile think the ship is in a particular place. At its most simplistic, the DRFM can transmit waveforms to make Nulka appear a more tempting target. This will cause the missile to lose its lock on the ship and pursue the decoy instead. Nulka decoys are already deployed by the RAN’s Hobart class destroyers, ANZAC class frigates and Canberra class amphibious assault ships.

This degree of commonality is important for two reasons: It creates economies of scale by having three ship classes all using the same AShM RF decoy type. Second, by deploying Nulka, the new frigates can provide overlapping AShM protection for other vessels in their locale.

Nulka decoy (US Navy)
One of the confirmed EW systems equipping the ‘Hunter’ class is the Nulka decoy soft-kill countermeasure. This is designed to lure an incoming radar-guided AShM away from the targeted ship.

Local Threats

Radar-guided AShMs are the predominant threat facing the RAN surface fleet. AShMs deployed with the People’s Republic of China’s (PRC) People’s Liberation Army Navy (PLAN) are the most worrisome. The PRC is also exporting AShMs around the Asia-Pacific region and further afield. Figures obtained by the author note that the PRC exported at least 112 AShMs to Burma and Pakistan between 2019 and 2020. These exports comprised exclusively China Aerospace Science and Industry Corporation (CASIC) C-802 (NATO reporting name CSS-N-8 Saccade) radar-guided AShMs. Over the same timeframe orders were concluded with Thailand for 80 CASIC C-708UNA submarine-launched AShMs. These will equip the Royal Thai Navy’s three forthcoming Chinese made Type-41/Yuan class conventional hunter-killer submarines.

A plethora of systems are either in service with the PLAN or are expected to enter service in the future. Of particular concern are the CASIC YJ-12 and Hongdhu Aviation Industry Corporation YJ-91. The latter is a Chinese version of Russia’s Tactical Missile Corporation’s Kh-31 (NATO reporting name AS-17 Krypton) AShM. Both weapons are reportedly capable of speeds exceeding 2,000 knots (3,704 kilometres-per-hour). The YJ-91 may even hit speeds of 3,000kts (5,557km/h).

The People’s Republic of China’s radar-guided anti-ship missiles are one of the most serious threats the RAN may have to contend with.
The People’s Republic of China’s radar-guided anti-ship missiles are one of the most serious threats the RAN may have to contend with.

Such speeds are of grave concern. They deprive a ship’s crew of valuable reaction time. To put matters into perspective, the YJ-91 has a reported range of 65 nautical miles (120 kilometres). The missile could cover this distance in circa 78 seconds. Rough measurements by the author reveal that the antennas for the Hunter classes’ CEA Technologies’ CEAFAR-2 S-band (2.3 gigahertz/GHz to 2.5GHz/2.7GHz to 3.7GHz) naval surveillance radar to be around 27.3 metres (89.6 feet) above the waterline.

Radars typically detect targets at a line-of-sight range from the antenna. Publicly available sources state that the YJ-91 has a sea-skimming altitude of 20m (66ft). The CEAFAR-2 could detect the missile at ranges of circa 16.2nm (30km). Nonetheless this would still give the crew a reaction time of a mere 19 seconds from detection to impact.

The Hunter classes’ ESM maybe able to extend this detection range a little further. ESMs tend to have a slightly longer detection range for a radar-equipped target, compared to a radar per se. However, this is unlikely to add more than a few seconds additional reaction time at best. A high reliance will therefore be placed upon the ESM detecting incoming radar-equipped targets before the CEAFAR-2.

CEA Technologies
CEA Technologies’ phased array radars are used on the ANZAC Class frigates, and will be used on the upcoming Hunter Class frigates, for which prototyping will start next year.

To further complicate matters, the radars equipping these missiles will almost certainly be transmitting Low Probability of Detection/Interception (LPD/I) waveforms. It will be imperative that the ESM can detect and recognise these LPD/I transmissions. These waveforms will typically be very discrete, hidden amongst the earth’s prevailing and omnipresent electromagnetic noise. They will enhance their discretion by using other LPD/I techniques like frequency hopping. Frequency hopping ensures that the radar’s transmissions do not remain on one frequency for more than a matter of milliseconds. The ESM will therefore need to include the latest electronic intelligence analysis software. This software will no doubt embrace techniques like Machine Learning and Artificial Intelligence (ML/AI). These will be key to performing the highly complex calculations required to rapidly recognise these radar signals. Capabilities which eclipse those of the human brain.

Once the radar and/or ESM determine that a radar-guided AShM is incoming, the ship will initiate its hard-kill and soft-kill response. The ESM will trigger an Electronic Countermeasure (ECM). This will either blind the missile’s radar seeker with noise, or lure it aware from the ship with deception jamming. The jamming maybe used alongside Nulka and conventional chaff countermeasures. Chaff uses thousands of metal strips cut to one half or one quarter the wavelength they are intended to jam. These strips are dispersed into the atmosphere. There, they form a cloud. These clouds are intended to fool the radar into thinking that it has found its target. Alternatively, the clouds may prove a more tempting target than the ship. Radar corner reflectors may also be used. These are inflatable dodecahedron shapes deployed on the surface some distance between the ship and missile. The sharp angular surfaces of the reflectors deflect the radar transmissions of the AShM away from its radar. This deprives the radar of a view of its target. Hard-kill countermeasures like Close-In Weapons Systems (CIWSs) will also be brought to bear. These will engage the missile with tens of rounds-per-second, shredding it into scrap metal. The Hunter class will be equipped with Raytheon’s Phalanx series CIWS.

There are two other major considerations for the Hunter classes’ EW systems. The first is saturation. A hypothetical confrontation between the RAN and PLAN would likely witness AShM salvo attacks by the latter. This would be done deliberately to overwhelm the hard- and soft-kill measures of individual ships. Both the ECM and ESM, alongside soft-kill decoys like Nulka will need to engage multiple, fast-moving incoming threats.

Second, the PRC is almost certainly equipping its state-of-the-art AShMs with Millimetric Wave (MMW) radar. Such radars transmit on frequencies of 30GHz and above. These radars transmit in wavelengths measured in millimetres. The short wavelengths of MMW transmissions provide highly detailed radar images for the missile. This means that the radar can match its radar picture with a preloaded radar image of the targeted vessel. This improves the weapon’s accuracy by helping it determine the optimum point of impact on the ship. It can also help the missile distinguish between decoys and the ship itself. The EW systems of the Hunter class will need to discern MMW radar transmissions and be capable of jamming these.


How much is the RAN likely to spend on the new frigates’ EW systems? The following figures assume that the new systems are bought off-the-shelf and adopted to Australian requirements. Developing new systems from scratch would incur significant additional costs. The author’s own figures note that, on average, a decoy launcher for a large surface combatant has an average unit price of $2.8 million. Assuming a minimum of two launchers equipping each vessel, decoy launcher expenditure per ship could be circa $6 million. This would result in around $18 million being spent on decoy launchers across the class of three ships.

Secondly, each ship in the class will have an ESM. These have an average unit price of circa $5.5 million. Therefore, the ESM fit across the fleet will be worth $16.5 million. The ESM will work with an ECM, the latter of which will have an average unit price of $1.9 million. This could result in a spend of $4.5 million across the class. Taking the cost of the decoy launcher, ESM and ECM together, the EW expenditure for each ship could be at least $12 million. Correspondingly this results in a possible $36 million of EW system expenditure across the class.

Next Steps

AMR contacted BAE Systems to ascertain timelines for the selection and installation of electronic warfare equipment for the Hunter class. The company directed all inquiries to the Australian Department of Defence (DOD). AMR contacted the DOD for the same information. No responses to our questions were received by the time we went to press. It is entirely possible that the DOD has yet to select the precise systems to equip the Hunter class. As of August 2021, it appears that the only system selected so far is Nulka. That said, work will continue defining the ship’s EW systems. We can expect further announcements to this effect in the coming months.

by Dr. Thomas Withington